core concepts-intro Flashcards
(18 cards)
what does a nucleoside consist of?
a nucleoside consists of a purine or pyrimidine base linked to the 1’ carbon of a pentose sugar
difference between DNA and RNA?
the difference between DNA and RNA is in the group at the 2’ position of the sugar. DNA has a deoxyribose sugar (2′–H); RNA has a ribose sugar (2′–OH).
what does a nucleotide consist of?
a nucleotide consists of a nucleoside linked to a phosphate group on either the 5’ or 3’ carbon the (deoxy)ribose
Successive (deoxy)ribose residues of a polynucleotide chain are joined
by?
Successive (deoxy)ribose residues of a polynucleotide chain are joined
by a phosphate group between the 3′ carbon of one sugar and the 5′
carbon of the next sugar
DNA bases names?
adenine, guanine, cytosine, and thymine
RNA bases?
rNA has Uracil instead of Thymine
What is the structure of B-form DNA?
It is a double helix made of two antiparallel polynucleotide chains.
How do the nitrogenous bases pair in DNA?
Adenine pairs with thymine (A-T), and guanine pairs with cytosine (G-C) via hydrogen bonds.
What is the diameter of the DNA double helix?
20 Ångströms (Å).
How many base pairs are there per turn in B-form DNA?
10 base pairs per turn (about 10.4 in solution).
What structural grooves are found in the DNA double helix?
A major (wide) groove and a minor (narrow) groove.
What does the one gene–one enzyme hypothesis state?
That each gene encodes one or more isoforms of a single polypeptide chain.
Do all genes encode polypeptides?
No, some genes encode structural or regulatory RNAs instead.
What effect do most coding sequence mutations have on gene function?
They damage gene function and are usually recessive to the wild-type allele.
How is the genetic code read?
In nonoverlapping triplets of nucleotides called codons, from a fixed starting point.
What is a frameshift mutation?
A mutation caused by the insertion or deletion of bases that shifts the reading frame of codons
What happens if three bases (or multiples of three) are inserted or deleted?
Amino acids are inserted or deleted, but the reading frame beyond that point remains unchanged.
